This invention relates to shelf-stable soil enrichment solutions containing Bacillus and other spores.
Where inoculations with microbes are required for agricultural uses such as soil enrichment, particularly enrichment of marginally suitable soils, control of insect pests, nematodes, and fungal disease, composting, and the like, dried preparations in the form of powders or granules are conventionally used because microorganisms lose viability in stored solutions. Typical liquid products containing microbes have an average short shelf life of only a few days to up to no more than about three weeks. Even so, liquid preparations are preferred for some applications because solutions are readily taken up by plants and can be formulated for controlled coverage by spray applicators. So solutions containing microorganisms are typically mixed just prior to use. See, for example, the addition of Streptomyces griseaviridis strains to aqueous suspensions in U.S. Pat. No. 4,595,589 to Tahvonen and Bacillus and Chlorella species to kelp extract products in U.S. Pat. No. 4,666,497 to Tenzer.
A number of attempts have been made to stabilize microorganisms in solution. Hettrick reported that reversible dormancy in a population of active microorganisms was achieved by adding diatomacious earth to the preparation (U.S. Pat. No. 3,898,132). Lewis disclosed ergot spore storage in at least about 25%, preferably between about 45 to 60%, by weight sugar solutions. In U.S. Pat. No. 4,161,397 to Bellet and Joshi, microdried bacteria were added to an oil carrier. In U.S. Pat. No. 5,366,532 to Fages, et al., microorganisms isolated from the rhizosphere such as Azospirillum lipoferum were microencapsulated in a polysaccharide matrix and packaged with a fertilizer.
Long-term storage stability in solutions at room temperature was apparently not achieved by these preparations, however. For example, the Fages, et al., results illustrate a viability decrease by a factor of five after 1 month of storage (column 3, line 43). Similarly, Barach and Kamara, who used polyethylene glycol or sodium alginate to stabilize acid-producing bacteria in buffer, typically observed a factor of 10 loss after 15 to 18 days (U.S. Pat. No. 4,720,460, column 5, line 68, column 6, line 44, and column 7, lines 11 to 12). In U.S. Pat. No. 3,999,973, Templeton disclosed a C. malvarum spore concentrate that maintained an 80% germination rate for up to 21 days if stored in ice.
It would be desirable to have soil enrichment solutions containing microorganism spores that remain viable for the shelf life of commercial stored agricultural products, i.e., at least about a year at room temperature.
It is an object of the invention to provide solutions that contain microorganism spores and/or colonies that remain viable for at least about a year when stored at room temperature.
It is another object of the invention to provide soil enrichment solutions containing viable microorganism spores and/or colonies, particularly those useful for enriching poor, disturbed soils or soils having little or no microbial activity because of the heavy past use of chemicals and/or fertilizers.
It is an additional object of the invention to provide solutions containing viable micro organism spores and/or colonies of beneficial fungicides that can be used for seed, turf, and leaf treatment for the prevention, control, and/or cure of turf and plant diseases and other beneficial purposes.
It is a further and more specific object of the invention to provide soil enrichment solutions containing microorganism spores and/or colonies that remain at least about 90% viable f or up to at least about 12, preferably 18 months at room temperature, i.e., about 20xc2x0 to 25xc2x0 C.
These and other objects are achieved by the present invention, which provides a method of preserving and solutions containing microbial spores and/or colonies comprising adding a microbial spore preparation such as lyophilized spores and/or colonies to a solution that is colloid al in nature and exhibits an ionic strength, water activity, and pH formulated to preserve the spores and/or colonies at room temperature. Typical soil enrichment solutions of the invention contain humic acids or another organic macromolecules such as methylene urea polymers having varying chain lengths that enhance spore/colony preservation. In some preferred embodiments, solutions of the invention are liquid fertilizers having a pH of less than or equal to about 3.5, and contain at least about 5% by weight humic acid or related macromolecules or other organic polymers, at least about 7% by weight cellulose fiber, at least about 1% carbohydrate, and at least about 1% by weight amino acids. The carbohydrates and amino acids are derived from plant extracts such as kelp extracts in some embodiments. Typical embodiments are formulated to deliver a range of from about 89 lb to about 176 lb nitrogen/acre/year for agricultural applications, and from about xe2x85x9 lb to about 1 lb nitrogen per 1000 square feet for turf applications, with a total of about 4 to about 6 lb applied annually.
Spores and/or colonies that enrich soils and/or provide plant biological control agents are employed in preferred embodiments. These include bacteria such as Bacillus species, e.g., Bacillus subtilis, Bacillus cereus, Bacillus penetrans, Bacillus licheniformis, and Bacillus megaterium; fungi such as Trichoderma, e.g., Trichoderma hamatum, Trichoderma harzianum, Trichoderma polysporum, Trichoderma konigii, Trichoderma viride; yeast such as Saccharomyces cerevisiae; and mixtures of these. Other examples are given hereafter.